Why do you have to get punished

Why Riot dosent punish a leaver not a guy with internet problems like lost connection but a actual leaver. i play top kench i go 4 0 i gank mid i gank bot 1 guy is arguing with a jungler my bot is 1 10 as usual i try to keep them motivated 1 disconects im like ok i can win this 4v5 they hunt low kills and surrender. And riot wont even check him out but yet you ban toxic people ? i this a nothing money grabing ponzi ? Ban ragers cause of evil people and make more money ? This game is turning into a COOP kindergarden simulator.